As a little girl, I always wanted a pony for Christmas. Santa never brought me a pony. So in my late 40s, I started taking horseback riding lessons. When I turned 50, I got my first horse, an Icelandic named Blessi (Veigar frá Búðardal). Little did I know how much fun life with an Icelandic was going to be. Blessi has a unique perspective on life. I hope you enjoy reading about it as much as I enjoy Blessi. And you will probably read about my cats from time to time.

Thursday, June 27, 2013

Genetic Basis of Gait in Icelandic Horse--Part 2

It is interesting to discuss the gaits the horse displays in the field
versus what they can do under saddle.
For example, I almost never see Blessi tolting in the field; he trots everywhere but he can do a nice pleasure tolt under saddle.

As the Andersson et al study states, "31% of the
four-gaited horses were homozygous A/A" so about 1/3 of the so-called
4-gaited horses in the study carried a homozygous A/A for the DMRT3 nonsense
mutation so were gentically 5-gaited. If this weren't true, there would be a
much higher percentage of
3-gaited Icelandics being bred.

Assuming
that AA represents 5-gaited horses, CA represents 4-gaited horses, and CC
3-gaited, the percentages of expected offspring are as follows (my interpretation was confirmed by a recent article in Equus Magazine):

AA (5-gaited) crossed with AA (5-gaited) = 100 %
5-gaited. Since only AA horses have a flying pace, this is how I can
interpolate that Blessi is 5-gaited.

So since
responsible breeders are eliminating the 3-gaited horses from the breeding
pool and knowledgeable breeders keep breeding back to 5-gaiters,
the percentage of 3-gaited horses is kept low.

Caution: In my 9th
grade science class, the teacher introduced genetics by talking about blue
eyes (bb) and brown eyes (Bb or BB). He told us that 2-blued eyed parents
could not have a brown-eyed child. I raised my hands and shared that my
parents both had blue eyes (really green) and my sister had brown
eyes (actually hazel). The teacher sputtered and went on to explain that eye
color is actually determined by multiple genes and the text book was
simplifying the matter. Of course, I took the text book home and told my
sister she was adopted.

Also this study adds additional credibility to
BLUP, which predicts which characteristics will be passed on to offspring.
For example, Blessi's BLUP predicts that, assuming he was still a stallion,
he would pass on the ability to pace, which I never understand since he was a
"4-gaited" horse. Now that I know a bit more about the genetics, I can
understand why BLUP would make this prediction.